Trigonella Foenum-graceum commonly known as Fenugreek is an herbaceous plant of the leguminous family and is native to Western Asia, from where it has spread widely over Europe, the Mediterranean and rest of Asia. It is one of the oldest cultivated plants and through the ages has found wide applications as a food, a food additive and as a traditional medicine in every region wherein it has been cultivated. The leaves and both the ripe and unripe seeds of Trigonella Foenum-graceum are used as vegetables. The seeds also function as a food preservative and are added to pickles, chutneys, and other similar food products. (Petropoulos G. A, “Fenugreek The genus Trigonella”, 2002, Taylor and Francis Publication, pp-9)
The ripe seeds have numerous applications in the traditional medicine system of India. Fenugreek has been used in treating colic flatulence, dysentery, diarrhea, dyspepsia with loss of appetite, chronic cough, dropsy, enlargement of liver and spleen, rickets, gout and diabetes. The seed is stated to be a tonic. It is also used in post-natal cure and to increase lactation in nursing mothers. (Al-Habori M. A et al “Fenugreek the genus Trigonella”, 2002, Taylor and Francis Publication, pp-162)
The different parts of Fenugreek seeds are indicated in FIG. 1. Fenugreek seeds are surrounded by the seed coat or the Testa (designated as 3 in FIG. 1). The seed coat is separated from the embryo (designated as 1 in FIG. 1) by a well-developed endosperm (designated as 2 in FIG. 1), which is the principal storage organ. In mature seeds the majority of the endosperm cells are nonliving, the cytoplasmic content of which are occluded by the store reserves viz galactomannan. Fenugreek seed contains a large number of compounds such as volatile oil, fixed oils, proteins, carbohydrates, dietary fibers, hemicellulose, galactomannans, cellulose, saponins, resins, pigments, vitamins, minerals and others.
Typical analysis results of fenugreek seeds are documented in the table 1 hereunder:
TABLE 1Typical analysis of fenugreek seedsCONSTITUENTPERCENTAGE1.MOISTURE9.02.ASH3.23.LIPIDS7.04.PROTEINS26.05.STARCH1.66.FIBER48.0Mucilage20.0Hemicelluloses17.3Cellulose8.2Lignin2.57.SAPONIN4.88.TRIGONELLINE0.37(Source: THE WEALTH OF INDIA, CSIR GOVT. OF INDIA PUBLICATION.)
Various seed components of Trigonella Foenum-graceum along with the dietary fiber have an important role in the treatment and management of several disorders such as obesity, coronary heart disease, diabetes, piles, fissures, chronic constipation and diverticulitis. The saponins are reported to contain active components that are anti-carcinogenic, anti-microbial and/or anti-oxidant.
The dietary fiber is the non-absorbable and indigestible fibrous portion, which is not assimilated by the body and is non-caloric and has substantially no nutrition value. It includes both soluble and insoluble fibers. Insoluble dietary fibers primarily comprise cellulose, lignin and some hemicelluloses; while soluble dietary fiber comprises pectin, gums and some hemicelluloses. (Evans A. J. et al, British J. Nut, 68(i), 1992, 217-229).
Owing to the versatile functionality of the various seed components of Fenugreek, attempts have been made to isolate these components using various processes. These processes primarily make use of organic solvents for extraction of the components. Majority of prior art teaches various processes of isolating a fraction that is rich in soluble dietary fibers. The particular emphasis for isolation of soluble dietary fiber is due to the physiological action of soluble dietary fibers, which makes them useful in the treatment of diabetes as well as obesity and other conditions (Sharma R. D., Eur. J. Clin. Nutr., Vol. 44, 1990, pp 301). Isolation of dietary fibers chiefly insoluble dietary fibers to arrive at a insoluble fiber rich fraction is of particular significance for the purpose of the present invention more particularly in establishing their hitherto untapped uses as pharmaceutical excipient.
Organic solvent-based methods for isolating soluble dietary fiber of the Trigonella Foenum-graceum seeds are known in the art.
Peter CHANG, in U.S. Pat. No. 5,997,877, discloses a process for isolation of oleoresins, saponins and a soluble dietary fiber. The process comprises of tempering fenugreek seeds to moisture level of 16-22%, followed by flaking using roller mill and sieving to separate the seed coat from cotyledon. The separated seed coat portion is treated with hot water for several hours, centrifuged and precipitated using a polar alcohol. Precipitate thus obtained is rich in soluble dietary fiber, which is further washed and dried.
Tempering/flaking before extraction is carried out to increase the extraction recovery ratio and decrease the contact times. To achieve proper tempering, seeds are mixed with water and kept aside for 24 hrs prior to flaking. The product so obtained is rich in soluble dietary fibers.
Flaking, which is an essential step for separation of seed coat from cotyledon in the disclosed process will not occur at ambient moisture content of fenugreek seeds. This makes the isolation process time intensive since tempering requires initial determination of the moisture content of the seed, followed by addition of a fixed quantity of water to achieve the desired moisture level uniformly. This not only increases the time of extraction process but also some times lead to hydrolysis of the lipids leading to discoloration of the final product as pointed out in U.S. Pat. No. 6,495,175.
In another embodiment of the same patent fenugreek seeds are treated with polar alcohols at high temperatures to isolate the oleoresin component prior to isolation of soluble dietary fiber; however the process may lead to loss of some amount of dietary fibers (Rao G. B. et al US patent application 20010024665A1). Dietary fibers are also further isolated by heating the fenugreek flakes with water at 60 degrees for 4 hrs which may affect the quality of the final product as well as the viscosity of the dietary fiber obtained.
Rao G. B. et al in U.S. Pat. No. 6,495,175 and US patent application 20010024665A1 describe a two step solvent extraction process wherein first extraction isolates fixed oils and second extraction isolates oleoresins leaving the light yellow to light brown dietary fiber. All of the above processes described in the prior art use high temperature, solvents and specialized extractor that makes the process very difficult on the commercial scale. Since the embryo is not separated from the dietary fiber at the time of grinding or isolation the fibers obtained have higher protein content, which is not a desirable attribute for use as a pharmaceutical excipient. The process disclosed in U.S. Pat. No. 5,658,571 by Gopalan et al also involves a special kind of reactor and solvents and has similar disadvantages.
Osband M. E. describes another solvent-based extraction process in PCT application WO9925197. The process results in a product having a high amount of protein (about 20-40%), which not only reduces the amount of dietary fiber content in the end product but also is undesirable for it to act as a pharmaceutical excipient.
BOURRET E., PCT application WO/0174371AI disclosed a method of using organic solvents to obtain Trigonella Foenum-graceum mucilage in the form of flour with grain size distribution less than 100 μm, consisting mannose, galactose, glucose, arabinose, xylose, rhamnose, D-galacturonic acid, galactomannans, and proteins. The key feature of the invention is pulverization of non-lipid fraction of fenugreek seed at sub zero temperatures (−195 degrees) to improve the solubility of non-lipid fraction of fenugreek seed in the extracting solvent. This requires a specialized facility to carry out such an operation and thus increases the cost of isolation of the dietary fiber.
U.S. Pat. No. 5,847,109 by Garti N. et al describes process of isolation involving use of organic solvents and high temperatures as well as specialized equipment for isolation of various components from fenugreek seed. Dietary fibers are also extracted using the same equipment and the same seeds following numerous treatments with different solvents. The process also involves treatment with polar alcohols, which may reduce the yield of the dietary fiber. The process yields dietary fibers with high protein content and to further reduce the protein content chromatographic techniques are suggested which are difficult and expensive to carry out at commercial scale.
PCT application WO 0128673AI describes the manufacture or isolation of galactomannans using various organic solvents, and the use of such galactomannans.
The prior art processes of isolation, as seen above are based on organic solvents, which may leave toxic residues and may pose problems during large scale handling. Moreover the time and technique intensive processes are cumbersome and costly at the same time are unable to result in desired quality dietary fiber.
Mechanical process of isolation has been described in the Japanese patent application JP 2001025265. The process involves special equipment comprising of a cylindrical vessel made up of metal net with 150 mesh screen and rotary wings for separating the endosperm. The seed of fenugreek are very difficult to pulverize and therefore keeping a 150 mesh screen means pulverization for a prolonged period leading to generation of local hot spots which may affect the properties of the final product. This process thus needs specialized equipment, and also there is a possibility that characteristics of the final product may be altered.
Prior art review shows attempts made to isolate the dietary fibers predominantly containing insoluble dietary fiber in higher purity are largely unsuccessful owing to non-specific isolation techniques, use of costly and specialized equipments, use of organic solvents for extraction and energy intensive methods. Moreover isolation of the dietary fibers was targeted more particularly to isolation of soluble dietary fibers for their therapeutic use or soluble dietary fibers with high protein content for nutritional purposes.
Prior art does not reveal any processes targeted towards maximizing isolation of insoluble dietary fibers with low protein content and high viscosity that can be used as a pharmaceutical excipient.
Although patents such as U.S. Pat. No. 5,288,618 by Hardin, U.S. Pat. No. 6,039,980 by Baichwal and U.S. Pat. No. 6,063,402 by Gebert describe pharmaceutical applications of galactomannan, none of these applications anticipate use of fenugreek galactomannan-fibers rich fraction as pharmaceutical excipient having high viscosity and binding properties. As a matter of fact, prior art teachings describe fenugreek as less efficient thickening agent (U.S. Pat. No. 5,847,109 and Brumer Y. et al, Food hydrocolloids, vol. 17(3), pp 229, 2003). It is particularly relevant to note that the prior art teaching of fenugreek as less efficient thickening agent undermines the effective use of the seed as pharmaceutical excipient while the present invention aims at providing fenugreek fiber rich fraction as a superior pharmaceutical excipient.